1. Field of the Invention
The present invention relates to motor vehicles and in particular to a method for controlling a fuel injector.
2. Description of Related Art
Methods of controlling a fuel injector have been previously proposed. Yaegashi et al. (U.S. Pat. No. 4,155,332) teaches an electric fuel injection system in an internal combustion engine. In the design of Yaegashi, a fuel control circuit operates a valve type injector. Yaegashi discloses a system for controlling a fuel injection based on information sent to a fuel control circuit via wires from an air flow meter, a pressure detector and an engine speed sensor.
In particular, an air intake value is measured using an air flow meter, and then compared with a pre-determined air intake quantity. If the air intake value is below the pre-determined value, the fuel injection quantity is calculated on the basis of the output signal from the air flow meter. If the air intake value is above the pre-determined value, the fuel injection quantity is calculated on the basis of the signal from a pressure detector and the engine speed sensor. A thermo sensor and an oxygen sensor are also are also connected to the fuel control circuit.
The operating logic of the system proceeds as follows: the intake air quantity is stored as datum W. Following this, the engine revolution count is stored as datum N. If W is greater than a pre-determined intake value Wa, then the injection quantity is calculated as W/N. Otherwise, the intake manifold pressure is stored as datum P and the calculation for the injection quantity is made based on P (manifold pressure).
While Yaegashi teaches an electronic fuel injection system that is responsive to an air flow quantity, the engine speed and the intake manifold pressure, Yaegashi fails to teach a fuel injection system that switches between a control method based on information from an air flow meter and a speed density control method. Yaegashi also fails to teach a fuel injection system capable of switching between more than two airflow control regimes.
Inoue et al. (U.S. Pat. No. 4,413,602) discloses a fuel injection control apparatus for an internal combustion engine. The fuel injection control apparatus of Inoue uses a first basic fuel injection signal for light load and a second fuel injection signal for heavy load. The fuel injection control apparatus includes multiple sensors: a throttle valve position sensor, a manifold pressure sensor and an engine pulse sensor. In the Inoue system, the engine load condition (light and heavy) is decided based on signals received at a selector by the throttle valve position sensor. Specifically, if the throttle valve angle is below a preset level, the engine load is defined as light. If the throttle valve angle is above a preset level, the engine load is defined as heavy.
When the engine is determined to be in light load, the basic fuel injection signal is determined based on the manifold pressure received by the manifold pressure sensor. Alternatively, when the engine is determined to be in heavy load condition, the basic fuel injection signal is determined based on the revolution number and the throttle valve angle as received from the engine pulse sensor and the throttle valve position sensor, respectively. Inoue also teaches a design in which the engine load condition is determined by the manifold pressure.
Inoue, however, does not teach a fuel injection control apparatus that uses an air flow meter for determining the fuel injection signal in some situations. Inoue does not teach a fuel injection control apparatus with a temperature sensor. Inoue also fails to teach or render obvious the concept of more than two engine loads.
Sawamoto (U.S. Pat. No. 4,450,814) teaches an air-fuel ratio control apparatus. Specifically, Sawamoto's design is directed at an internal combustion engine with a turbocharger. The air-fuel ratio control apparatus selects between two methods for calculating a fuel injection quantity based an intake vacuum pressure parameter.
Normally, the controller controls the amount of fuel injected according to input received by an air flow meter and ignition coils (which sense engine speed). If the intake vacuum pressure as measured by the pressure sensor is higher than a pre-determined value, the fuel quantity is then calculated from the engine speed only.
While Sawamoto does teach an air-fuel ratio control apparatus with two distinct methods for calculating a fuel injection quantity, Sawamoto fails to teach an apparatus that incorporates a temperature sensor within the intake manifold for facilitating the calculation of the fuel quantity. Additionally, Sawamoto fails to teach more than two regimes of air flow where different methods of calculating a fuel injection quantity may be applied. Finally, Sawamoto fails to teach an apparatus in which the transition criteria is based on multiple factors (such as throttle valve angle and engine speed in addition to intake manifold pressure).